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- Welcome to the Exploratorium. I'm Hilleary Osheroff, biologist and educator here in the Exploratorium's Teacher Institute. The Exploratorium's exhibits are the foundation of our work, and they're designed to provide visitors the opportunity to investigate phenomenon and figure things out for themselves. Today, I'm going to show you one of my favorite exhibits, called Bacteriopolis, and show you how to make your own at home. Look carefully at this wall behind me. What do you notice? This wall may look like it's made of paint or minerals, but these colorful patches are actually living things. You can't tell this in one visit to the Exploratorium, but over time, these patches change and grow. Each color that you see here is actually a colony or cluster of bacteria growing in soil, and they've been living in this exhibit for years. They originally came from some mud from Golden Gate Park, just across the city. This exhibit is actually a huge version of an experiment called Winogradsky column, which is a bacterial culture from soil placed in a self-contained environment. It's named for the scientist that originally invented this method of growing and studying bacteria. Making your own is actually really, really simple. We have instructions for how to make this on our Science Snack website, where we have hundreds of science experiments and activities, which we call Science Snacks, all of which you can do at home. To make your own Winogradsky column, all you need to do is put some mud into a clear container, provide it with light, air and water, and wait to see what happens. The bacteria in this column are biochemically and metabolically incredibly diverse. They get their energy from all different sources. Some of them are a little bit like you. They ingest and break down carbon compounds made by other species in the column to get their energy, almost like they're eating each other. Others get their energy in a completely different way, by doing reactions with minerals like sulfur and iron. Many of these bacteria get their energy from sunlight. They're photosynthesizers, like some of these green colonies near the top of the column. As byproduct of photosynthesis, they produce the oxygen gas that we breathe. And microorganisms like these actually completely transformed our planet's environment a few billion years ago, creating the oxygen-rich atmosphere that we depend on to live. There's also other bacteria in this column that photosynthesize, but don't produce oxygen. These are anaerobic photosynthesizers and they tend to be found near the bottom of the column. You might be wondering, what's with all the different colors? Many of these colors come from molecules that help these diverse photosynthesizers capture light energy. Some of these molecules have a special property which is that they fluoresce. That means when you shine a far blue or UV light on them, they absorb that light and re-emit it at a different wavelength, producing a reddish magenta color. So I like to use a special tool at this exhibit, a UV flashlight, which provides this far blue wavelength. We tend to think of photosynthesizers as being green, like plants. But in fact, they can contain many different pigments, and some colonies that aren't green still fluoresce, meaning they're probably photosynthetic. This is a mini version of Bacteriopolis that I made a few years ago with mud from the bay underneath Pier 15. I keep it in a sunny window, and it's been growing and changing for about three or four years now. Winogradsky column isn't just cool to look at, it captures what happens in soil and mud in nature and it allows researchers to figure out which bacteria are doing what. It can even be used to test how climate change might affect the natural recycling processes happening in soil. How do you think the bacteria that are found in mud from a pond or stream might be different from the bacteria found in the mud from the shore of a bay or ocean, or a mud puddle? What beautiful, biochemically diverse bacteria are living in your backyard or in the neighborhood park? Make your own Bacteriopolis, and find out.